Very accurate positioning of an object such as a workpiece or a tool is a fundamental requirement of all product-shaping and deposition mechanisms. Rather large dimensional tolerances on the order of thousandths of an inch have been tolerable for many years, and for a wide range of products they still are. However, newer products, especially in the microelectronics field require that manipulations be held to much closer tolerances, often in the realm of a few microns.
The problems one faces with these new requirements cannot readily be solved by the older approach of better linear guideways and bearings. These all have their own tolerance problems, which are amplified when many of them are involved in the manufacture of the same product. The result has been production equipment which, while made to the best standards attainable with existing approaches, still limit the quality of product that can be produced by them, and increase the scrap rate of a production run.
A large part of this problem resides in the structural support and physical guides required to move and position the tool or the workpiece. Conventional dovetails, rails and rotary bearings all involve problems such as linear runout and backlash that can result in inaccuracies on all six degrees of freedom.
This invention proposes the use of an entirety different positioner which may be thought of as a “motion stage”. It prevents motion on five of the six possible degrees of freedom, and severely restrains movement of the stage to the sixth degree. The six degrees of freedom are defined as axial motion along the X, Y and Z axes, and rotation around each of them. In this invention, the single degree of freedom enjoyed will generally be axial along the Z axis. Then axial movement along the X and Y axes, and rotation around any of the X, Y and Z axes is prevented. The Z axis is commonly regarded as the vertical axis. This terminology is used herein for convenience. However, with this invention the Z axis may be directed in other directions, for example horizontally or at an angle to the vertical.
In contrast to the very costly mechanisms presently available for accurate single axis positioning, it is an object of this invention to use simple rotors and flexures that do not involve sliding motion and which inherently prevent twisting, shear, and lateral movement.
It is another object of this invention to provide the positioner as a passive element which permits accurate movement of the stage only along the allowed axis in response to forces exerted along it.
It is another object of this invention to provide the positioner as a product which employs simple flexures and rotors that can readily be manufactured to produce a surprisingly affordable, accurate and useful product.
It is yet another object of this invention to provide a positioner that can be used in a severe vacuum, there to operate efficiently without shedding of particulates or lubricants that could foul the vacuum environment. It inherently does not require lubrication, for example.
It is still another object of this invention to provide guidance for a system in which relatively crude motion means can be used, still to provide such accuracy. For example, an inflatable bladder can be used.